1. Field of the Invention
The present invention relates to 4-chloro-3,5-diaminophenyl acetates, preparations thereof and curing agents for polyurethane elastomer using the same compound.
2. Description of the Prior Art
It has been well known that aromatic diamines are used as curing agents for polyurethane elastomer. Various aromatic diamines have been proposed. However, various characteristics have been required for curing agents used for polyurethane elastomer and satisfactory aromatic diamines could not be obtained. The characteristics required for curing agent include
(1) low melting solid or liquid from the viewpoint of processability and labour hygiene and saving of energy;
(2) suitable pot-life as a time from mixing the curing agent with a mixture of polyisocyanate and polyol or a prepolymer having terminal isocyanato group to lose fluidity in a casting, from the viewpoint of processability;
(3) suitable set time as a demoldable time from pouring the mixture to taking out the casted product from the viewpoint of processability especially efficiency;
(4) easy synthesis and stability of the object curing agent; and
(5) formation of a cured polyurethane elastomer having excellent mechanical characteristics.
These characteristics are inconsistant each other, for example, a trouble of processing is caused by a short pot-life when a short set time is expected. It has been difficult to obtain a curing agent having suitable balance for satisfying these required characteristics.
For example, 3,3'-dichloro-4,4'-diaminodiphenyl methane is a curing agent for polyurethane elastomer having excellent mechanical characteristics, however, it has high melting point (100.degree. to 106.degree. C.) whereby the processability is disadvantageously inferior.
It has been known that 4-chloro-3,5-diaminobenzoates are curing agents for polyurethane elastomer having excellent mechanical characteristics which has long pot-life but the set time disadvantageously is long and a melting point is mostly high. (Japanese Patent Publication No. 51959/1972).
The inventors have studied to obtain a curing agent which has the satisfactory characteristics required for the curing agent for polyurethane elastomer and have synthesized many compounds.